In a recent post, I discussed some reasons why political polarization has become much worse in recent years.  In the comment section, I was startled to see people deny that polarization had actually become much worse.  (Perhaps some commenters are too young to recall the 20th century.)  In any case, a recent article in The Economist provides some data: Scholars of American politics are particularly dismayed by rising levels of “affective polarisation,” the political science term for the hostility one...